Peridinium gutwinskii (Dinophyceae) from Angola: diagnostic features and worldwide morphological variability of the species

Peridinium gutwinskii Wołoszyńska is a freshwater dinoflagellate with a complex and variable thecal plate morphology presenting some problems for taxonomic delimitation. In this study, we document the occurrence of P. gutwinskii in central Angola, extending its known distribution in tropical Africa. Detailed observations using scanning electron microscopy revealed specimens with a pentagonal 2a intercalary plate, a lobed 7'' plate, a keel-shaped hypotheca, and the presence of an antapical fin, all features that differ from the original description, but closely resemble material previously reported from Argentina. Comparative analysis of published records indicates that these and other morphological traits occur in diverse combinations across populations, suggesting that they represent intraspecific variability rather than diagnostic differences. Our analysis highlights the limitations of relying solely on one morphological characteristic for species delimitation in Peridinium and emphasizes the need for molecular data to clarify whether the observed variation reflects phenotypic plasticity or cryptic diversity. Until such evidence is available, recognition of P. corrientes Moestrup as distinct from P. gutwinskii should be treated with caution.